over, many times completely. This means that there is vast seasonal lag offshore such as on the island of Rödkallen on the Swedish side. Due to the mild nature of summers and the low diurnals, offshore islands tend to be humid continental since September usually stays above means. Ecology The Quark ridge at the south of the bay defines the dividing line beyond which many salt water species are unable to survive. Instead of the red and brown algae found further south, the bay has predominantly green algae and phanerogams. Annual plant species are almost completely dominant. The only perennials are a few specimens of the freshwater cryptogam Isoetes echinospora and the moss Fontinalis dalecarlica. Often the green algae have a dense covering of epiphytic diatoms. The shores, beaches and shallows include a variety of northern plant species including the endemic yellow hair grass (Deschampsia bottnica). The only filter feeders are Ephydatia and, at the river mouths, small numbers of freshwater mussels. Bivalves make up 9% of animal biomass. Crustaceans, mostly Saduria entomon make up 45% and gastropoda 30%. The gastropoda are grazing snails related to freshwater species. Fish species found in the area's lakes and rivers also live in the bay, including roach, perch, pike and grayling. Ringed seal, grey seal, cod, herring and salmon may also be found in the bay. In the 16th century seals were hunted in the Bay of Bothnia. Ringed seals were captured using nets in the inshore open water, and were stalked and captured in their dens or at breathing holes. Both grey and ringed seals were hunted along the edge of the ice. Wild vendace roe harvested from the Kalix River, known as Kalix Löjrom or as sea gold, is a delicacy with a European protected designation of origin. Birdlife includes the black guillemot, velvet scoter, oystercatcher, lesser black-backed gull, western capercaillie and willow ptarmigan. Moose and hare are found on the islands, as on the mainland. Occasionally, whales have been observed in Bothnian Sea and remains of extinct Atlantic gray whale was found from Gräsö while it is not clear whether or not whales might once have reached Bothnian Bay historically. Population Ports on the Finnish side include Haukipudas, Jakobstad, Kemi, Kokkola, Oulu, Raahe and Tornio. The largest towns by population on the Finnish side as of 2013 were Oulu (192,680), Tornio (22,374), Kemi (22,157), Kempele (16,549), Raahe (25,641), Kalajoki (12,637),